Objective In a recent consensus statement on early pregnancy nomenclature by Barnhart, a definite ectopic pregnancy (EP) was defined morphologically on transvaginal sonography (TVS) as an extrauterine gestational sac with yolk sac and/or embryo, with or without cardiac activity, whilst a probable EP was defined as an inhomogeneous adnexal mass (‘blob’ sign) or extrauterine sac‐like structure (‘bagel’ sign). This study aims to determine whether these ultrasound markers used to define probable EP can be used to predict a definite tubal EP. Methods This was a retrospective cohort study of women presenting to the Early Pregnancy Unit (EPU) at Nepean Hospital, Sydney, Australia between November 2006 and June 2016. Women classified with a probable EP or a pregnancy of unknown location (PUL), i.e. with no signs of extra‐ or intrauterine pregnancy (IUP), at their first TVS were included, whilst those with a definite tubal EP, IUP or non‐tubal EP were excluded from the final analysis. The gold standard for tubal EP was histological confirmation of chorionic villi in Fallopian tube removed at laparoscopy. The performance of blob or bagel sign on TVS in the prediction of definite tubal EP was evaluated in terms of sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). This was compared with the performance of extrauterine gestational sac with yolk sac and/or embryo on TVS to predict definite tubal EP. Results During the study period, 7490 consecutive women attended the EPU, of whom 849 were analyzed. At primary TVS, 240/849 were diagnosed with probable EP, of which 174 (72.5%) were classified as blob sign and 66 (27.5%) as bagel sign. The remaining 609/849 were diagnosed with PUL, of which 47 had a final diagnosis of EP (including 24 blob sign, 19 bagel sign and four gestational sac with embryo/yolk sac). 101 of all 198 (51%) blob sign cases and 50 of all 85 (59%) bagel sign cases underwent laparoscopy and salpingectomy; histology proved a tubal EP in 98 (97%) of these blob‐sign cases and 48 (96.0%) of the bagel‐sign cases. The sensitivity for the blob and bagel signs in the prediction of definite tubal EP was 89.8% and 83.3%, respectively, the specificity was 99.5% and 99.6%, PPV was 96.7% and 95.2% and NPV was 98.3% and 98.6%. This was comparable to the sensitivity of extrauterine gestational sac with yolk sac and/or embryo on TVS in the prediction of definite tubal EP (sensitivity, 84.0%; specificity, 99.9%; PPV, 97.7%; NPV, 99.3% (P = 0.5)). Conclusions Blob and bagel signs seem to be the most common presentations of a tubal EP on TVS. Although they cannot be considered as a definitive sign of EP, their PPV is very high (> 95%); such women should therefore be considered at very high risk for having a tubal EP and should be treated as such. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.